Before the administrative re-organisation of 1974, the parish of Llanrhaeadr yn Mochnant consisted the Denbighshire townships of Banhadla Ucha, Banhadla Isa, Gartheryr, Henfachau, Trebrys Fawr, Trebrys Fach, Trefeiliw, Tre'r-Llan and Tre-Wern; and the Montgomeryshire townships of Abermarchnant, Brithdir, Castellmoch, Cefn Coch, Glanhafon Fach, Glanhafon Fawr and Nantfyllon.
St. Dogfan's church was mentioned in the Norwich Taxation of 1254. It was restored between 1879 and 1882.
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For family history information about the church and parish, visit the GenUKI Llanrhaeadr ym Mochnant page.